For a long time, I knew that when a book was dog-eared, it was not only worn but also abused in some way. However I did not know that the abuse took a specific form: the turning down of the corner of a page, most likely as a quick way to mark thepoint at which you stopped reading. To dog-ear is to make a cheap and abusive bookmark. The description is based on the visual similarity of a turned down page to a dog's ear, which tends to flap over. That makes this a predominantly visual metaphor.

Dog-eared (adjective) Though the OED does not mention it, other things can be dog-eared besides books. At first I inferred that the adjective can be applied to any well worn and (ab)used item. In referring to the shopping cart of an elderly Dubliner, AP writer, Shawn Pogatchnik, described it as “her dog-eared blue-leather trolley.” However, I discovered that dog-earing can aslo be a characteristic of fabric. Tom Burns Haber refers to George Linton's Modern Textile Dictionary, which states that dog-earing refers to “A defect in cloth that tends to roll or curl up at the corners.”